I live in South Jersey and am looking to disappear into Pennsylvania from this coming Thursday until the Thursday after. The catch is that I'm on a shoestring budget and would like to find a way to reach a trailhead without having to spend $100 on gas/tolls.

Thus my question: Are there any ways to get to Allegheny NP or a good swathe of state forest land solely via public transit (or a conveniently-timed rideshare) from Philly?

You may have already thought of this, but you could take the Bolt Bus / Mega Bus from 30th Street in Philly to Harrisburg/State College/Pittsburgh. I realize from those locales you'd probably have to take another form of transportation to a trail head but maybe you know someone in one of those areas that could shuttle you.

Another option I thought of was the Bolt Bus from the Cherry Hill Mall to NYC and then the Trailways Bus to the Catskills at Woodstock, NY. Would probably still cost around $100 round trip though.

Could stay local and hike the Batona Trail through the Pinelands but that's neither disappearing nor would it take more than a couple days.

There's a Metro North stop on the AT in Pawling, NY too but you'd still have to get to NYC first.